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Smog Fail Help

hiimmred

hiimmred

NAXJA Forum User
Location
San Bruno, California
Seems to be running rich. '90 4.0 auto. 237k miles. Cat is about a year and a half old. Don't want to put another on while it's running rich if it's going to go bad in a few months.

Results:
%CO2 15/25mph = 14.0/14.0.
%02 15/25mph = 0.0/0.0.
HC (ppm) 15/25mph = 134/130. Max allowed = 123/103.
CO (%) 15/25mph = 1.47/1.50. Max allowed = 0.73/0.93
NO (ppm)15/25mph = 910/881. Max allowed = 711/613.

Any thoughts/solutions are greatly appreciated.

Thanks,
Mr. Ed
 
The most commonly overlooked sensor on the Renix is the air charge temp sensor on the intake manifold just rearward of the throttle body. It can be checked with an ohmmeter and will cause it to run rich.
 
Lambda calculator says really rich, .95 . Have you checked your o2 sensor?

I have a good one at work if you need it Ed.
 
old_man said:
The most commonly overlooked sensor on the Renix is the air charge temp sensor on the intake manifold just rearward of the throttle body. It can be checked with an ohmmeter and will cause it to run rich.
Click to expand...

X2

While he is at it, he should test the O2 sensor, live, with an analog volt meter. Test the O2 sensor heater for resistance, and test for power to the heater on the O2 sensor. Testing the CTS would be a good idea too, it has the resistance versus temp readings as the MAT (ACT, IAT, sensor, has more names than my cat has lives it seems) M=manifold, A=Air, I=Intake,

Also run some injector cleaner in the gas and directly into the throttle body (like carburator cleaner, Gumout....) to get rid of carbon build up in the head and valves, that raises the NOx numbers.
 
if was sticking in open loop or just reading too cold it might run righ. how is the coolant temp sensor? they are under the exhaust manifold?

what about the MAP sensor? have you tested it for voltage.
the sensors that id be concerned with:
02 sensor
mat(air charge sensor/manifold absolute temp sensor , same thing)
MAP
coolant temp sensor
TPS
they all contribute to the computer determining the air fuel ratio...

check for vacuum leaks and intake/exhaust leaks as well(pre-02 sensor exhaust leaks).

how are your grounds? cleaned them recently? bad grounds ca cause good sensors to read off...

i seafoamed the intake on both my XJ and 4runner before SMOG this year, as well as letting it warm up for 30 mins. they both passed with flying colors. i have a renix as well....
 
Thanks for the input everyone, o2 sensor was replaced at the same time as the cat, both have less than 5k on them. I'm not adept at checking sensors although I do have a multimeter. Anyone local have some time and experience to assist?
 
i was closer or if i am out there anytime soon ill bring my multimeter and my supersized chiltons. they are fairly straight forward if you have the chiltons.
less than 5k on cat and 02 sensor.
by chance do are you missfiring?
a stuck open injector could cause a misfire?
run a bunch of injector cleaner through tank and seafoam intake?
run some MMO in the oil(or tranny fluid) to clean out what you can while youre at it.

do you have any random shots of high revolutions? like at start up or while driving?
if not the TPS is most likely good.

i had a cracked vacuum line to the MAP SENSOR before. if you fully disconnect the map sensor vacuum line it wont even run.

have you checked fuel pressure just for the hell of it?
made sure the exhaus manifold bolts are all tight?
and grounds?
 
Fairly new TPS, I do have a broken exhaust manifold bolt at the rear. Of course it's raining today so I'm not going to get much into it until next Saturday. Recently replaced all injector O-rings. Have ran cleaner and MMO every few tanks. I think it may be misfiring on occasion but minimally. The plugs, wires and cap have all been replaced in the last 7500 miles.
 
hiimmred said:
Fairly new TPS, I do have a broken exhaust manifold bolt at the rear.
Click to expand...

Ah, such a trivial thing, why even mention it, LOL!:laugh2:


:banghead::banghead::banghead:
 
the broken bolt will cause the others to come loose over time and cause a bigger exhasut leak...over a long enough time youll need to replace the gasket easily...

i would say replace the exhaust manifold gasket and try to get a new bolt in there.
i have a broken stud in the front of mine, it still smogs just fine, i used copper rtv on both sides of the exhasut manifold gasket as well as filling in the hole with the broken stud. tried to extract it and broke a super hardened bit in the stud. exhasut manifold gasekts are easy and cheap to replace....

misfire could be stuck open injector? bad ground, etc...
 
So I checked the exhaust and a couple bolts were a little loose but not much. Went to a friends shop and threw the OBD1 scanner on it and it appears the O2 sensor is staying at a constant 4.98v and the system stays in open loop. The EGR is functioning okay. I'm surprised the O2 is bad as it is only a couple years old and I haven't put that many miles on it since. All the other sensors appeared to be functioning properly.
 
Did you check to see if the third wire was getting voltage for the heater inside the O2 sensor?

As I said previously: "While he is at it, he should test the O2 sensor, live, with an analog volt meter. Test the O2 sensor heater for resistance, and test for power to the heater on the O2 sensor"

The third wire, the large orange one should 5 or 12-14 volts on it at the sensor, and the power off orange wire from the O2 sensor to ground should read about 8 ohms.
 
coolant temp sensor?
 
With Renix, a working O2 sensor, working MAT and MAP sensor should over ride bad CTS data once running.
 
good to know.
 
hiimmred said:
Seems to be running rich. '90 4.0 auto. 237k miles. Cat is about a year and a half old. Don't want to put another on while it's running rich if it's going to go bad in a few months.

Results:
%CO2 15/25mph = 14.0/14.0.
%02 15/25mph = 0.0/0.0.
HC (ppm) 15/25mph = 134/130. Max allowed = 123/103.
CO (%) 15/25mph = 1.47/1.50. Max allowed = 0.73/0.93
NO (ppm)15/25mph = 910/881. Max allowed = 711/613.

Any thoughts/solutions are greatly appreciated.

Thanks,
Mr. Ed
Click to expand...

Replaced the O2 sensor (thanks Bryan C.) and my junk passed and lives on to spend another year on the rocks!
New numbers:
%CO2 15/25mph = 14.9/14.9.
%02 15/25mph = 0.1/0.0.
HC (ppm) 15/25mph = 30/18. Max allowed = 123/103.
CO (%) 15/25mph = .09/.03. Max allowed = 0.73/0.93
NO (ppm)15/25mph = 278/209. Max allowed = 711/613
 
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